Method for monitoring brake dragging of an elevator

Abstract

A method includes calculating a motor torque estimate for an electric motor of an elevator in an elevator run, determining a difference between the calculated motor torque estimate and a realized motor torque during the elevator run, and generating a signal indicating possible brake dragging based on the difference between the motor torque estimate and the realized motor torque.

1 . A method for monitoring brake dragging of an elevator, the method comprising the steps of:
 calculating a motor torque estimate for an electric motor of the elevator in an elevator run;   determining a difference between the calculated motor torque estimate and a realized motor torque during the elevator run; and   generating a signal indicating possible brake dragging based on the difference between the motor torque estimate and the realized motor torque.   
     
     
         2 . The method according to  claim 1 , wherein the signal indicating possible brake dragging is generated based on the magnitude of the difference between the motor torque estimate and the realized motor torque and based on the duration of said magnitude. 
     
     
         3 . The method according to  claim 1 , wherein the signal indicating possible brake dragging is generated when the difference between the motor torque estimate and the realized motor torque meets or exceeds a predetermined threshold for a predetermined time period. 
     
     
         4 . The method according to  claim 1 , wherein the signal indicating possible brake dragging is generated when the difference between the motor torque estimate and the realized motor torque meets or exceeds a first predetermined threshold for a first predetermined time period or when the difference between the motor torque estimate and the realized motor torque meets or exceeds a second predetermined threshold for a second predetermined time period, the value of the second threshold being lower than the value of the first threshold and the second time period being longer than the first time period. 
     
     
         5 . The method according to  claim 1 , wherein the motor torque estimate is calculated based on all or of any combination of the following criteria: the rated load, the output of the load weighing device, the balancing percent and the compensation, the position of the dependent masses, the total moving masses, the shaft efficiency, and the acceleration reference. 
     
     
         6 . The method according to  claim 1 , wherein the realized motor torque is the output of the speed control in a speed control circuit. 
     
     
         7 . The method according to  claim 1 , wherein the signal indicating possible brake dragging based on the difference between the motor torque estimate and the realized motor torque is transmitted to a remote service centre. 
     
     
         8 . A brake monitoring apparatus, comprising:
 a drive unit configured to drive an elevator car; and   a controller comprising an elevator speed control circuit,   wherein the controller is configured to perform the method according to  claim 1 , and   wherein the brake monitoring apparatus further comprises a signal generator configured to generate a signal indicating possible brake dragging.   
     
     
         9 . An elevator comprising the brake monitoring apparatus according to  claim 8 . 
     
     
         10 . The elevator according to  claim 9 , wherein the elevator comprises a remote communication link to a remote service centre. 
     
     
         11 . A computer program product embodied on a non-transitory computer readable medium and comprising program instructions, which, when run on a computer, causes the computer to perform the method as claimed in  claim 1 . 
     
     
         12 . The method according to  claim 2 , wherein the motor torque estimate is calculated based on all or of any combination of the following criteria: the rated load, the output of the load weighing device, the balancing percent and the compensation, the position of the dependent masses, the total moving masses, the shaft efficiency, and the acceleration reference. 
     
     
         13 . The method according to  claim 3 , wherein the motor torque estimate is calculated based on all or of any combination of the following criteria: the rated load, the output of the load weighing device, the balancing percent and the compensation, the position of the dependent masses, the total moving masses, the shaft efficiency, and the acceleration reference. 
     
     
         14 . The method according to  claim 4 , wherein the motor torque estimate is calculated based on all or of any combination of the following criteria: the rated load, the output of the load weighing device, the balancing percent and the compensation, the position of the dependent masses, the total moving masses, the shaft efficiency, and the acceleration reference. 
     
     
         15 . The method according to  claim 2 , wherein the realized motor torque is the output of the speed control in a speed control circuit. 
     
     
         16 . The method according to  claim 3 , wherein the realized motor torque is the output of the speed control in a speed control circuit. 
     
     
         17 . The method according to  claim 4 , wherein the realized motor torque is the output of the speed control in a speed control circuit. 
     
     
         18 . The method according to  claim 5 , wherein the realized motor torque is the output of the speed control in a speed control circuit. 
     
     
         19 . The method according to  claim 2 , wherein the signal indicating possible brake dragging based on the difference between the motor torque estimate and the realized motor torque is transmitted to a remote service centre. 
     
     
         20 . The method according to  claim 3 , wherein the signal indicating possible brake dragging based on the difference between the motor torque estimate and the realized motor torque is transmitted to a remote service centre.